Applications and problems of parametric counting

Abstract

The large and expanding field of modern high technology based upon silicon and its compounds is ideally suited for INAA using parametric counting, since neither the silicon nor the impurities present in almost infinite dilution give rise to self-shielding effects. Parametric counting, however, requires a fast and convenient method for determining the thermal, resonance, and fast neutron fluxes during irradiation. The resonance flux should be measured close to 5 eV, because most of the analytically important isotopes with large Ip/σo values have their resonance energies in the 1–15 eV region, and because the resonance flux in a commercial reactor does not follow the theoretical 1/E distribution in energy. It is shown in this paper that the resonance flux as measured with the “zirconium method” is practically identical to the resonance flux obtained from cadmium ratio measurements on gold. In addition, the zirconium monitor also yields the thermal and fast fluxes, and has several practical advantages, especially for longer irradiations.